I. Field of the Invention
This invention relates generally to implantable tissue stimulating apparatus, such as cardiac pacemakers, cardiac defibrillators and related devices, and more particularly to an improved method of securing the proximal terminal pin and ring of the stimulating lead in the female jacks of the electrical stimulating pulse generator.
II. Discussion of the Prior Art
Implantable stimulating devices, such as cardiac pacemakers, automatic implantable cardiac defibrillators, and myostimulators generally comprise electronic sensing and pulse generating circuitry and associated power sources housed within a body member formed from a suitable metal and commonly referred to as the "can". Passing through the can's top surface in a hermetically sealed manner are electrical feed throughs, which are arranged to conduct electrical signals into and out from the circuitry sealed within the metal can. Affixed to the top surface of the can and surrounding the feed throughs is a molded plastic body having one or more longitudinal bores formed therein for receiving the proximal end male connector of the implanted flexible leads used to convey electrical stimulating pulses from the implanted pulse generator to the tissue to be stimulated and for conveying physiologic signals or myopotentials picked up by the lead's distal electrodes and carried back to the pulse generator electronic circuit. The bores in the body member communicate with electrical contacts that mate with pin and ring-type connector terminals on the proximal end of the leads. Typically, setscrews or other threaded fasteners pass through threaded bores oriented transverse to the lead receiving bores in the body member and in the connector block to maintain the lead's proximal terminal pin and ring in fixed or locked relation relative to the connector blocks coupled to the feed throughs in the body member of the pulse generator.
A typical example of the prior art lead connection heretofore used in the cardiac stimulating field is shown in the Ware U.S. Pat. No. 4,142,532 which, in FIG. 2 thereof, shows a can 13 with feed throughs 19 embedded in a molded plastic header 25, the feed through being electrically coupled to a terminal block 40 having longitudinal bores 41 and 45 formed therein for receiving electrical leads having pin and ring-type male terminals 21 surrounded by an insulating sheath 22 preferably formed from silicon rubber or other suitable medical grade plastic. A setscrew 47 threaded into the terminal block 40 is designed to engage the terminal pin 21 to firmly lodge it in place. Plugs 48 then fit into the screw axis holes 53 to preclude the influx of body fluids and/or body tissue.
Other examples of the prior art similar to the disclosure of the Ware U.S. Pat. No. 4,142,532 described above are the Kinney et al. U.S. Pat. No. 4,262,673 and the Anderson et al. U.S. Pat. No. 4,072,154.
While the prior art techniques for securing stimulating leads to implantable pulse generators have proved reliable, they suffer from the defect that they require the attending physician to handle small parts, such as the setscrews and the seal plugs and also require the use of a screw driver or an allen wrench to install and tighten down the setscrews onto the lead's terminal pins. Thus, a need exists for a method of coupling the proximal terminals of cardiac stimulating leads to an implantable pulse generator which does not require the handling of small parts or the use of special tools to perfect the connection. The Peers-Trevarton U.S. Pat. Nos. 4,540,236 and 4,784,141 each describe quick-lock/quick-release connectors for implantable cardiac stimulators, but in each instance, a special, non-standard lead is involved. For example, in the '236 patent, the lead incorporates a plunger body 34 on the proximal end of its terminal pin and the plunger fits into a socket having a plurality of spring fingers for effectively gripping the plunger body. The device can be released by pressing on an elastomeric diaphragm 40 which serves to move the plunger and spread the spring fingers so that they no longer lock relative to the terminal pin. The mechanism described in the Peers-Trevarton patents are unduly complex and, hence, may prove unreliable with time.
It can be seen, then, that a need still exists for a way of rapidly and reliably coupling standard implantable stimulating leads to its associated pulse generator in a way that will reduce the surgeon's time and undue complications for making this connection while eliminating the setscrews, seal plugs and a special setscrew wrench. Moreover, the approach used must preclude an electrical leakage path occasioned by body fluid seepage into the lead to feed through coupling zone.